U5: CHROMOSOMAL ABERRATIONS + DELETION Flashcards
Tiny changes in the chromosome
Mutations
Structural or numerical change in the chromosome seen even in simple staining techniques
Aberrations
Test for copy number repeats or loss
CGH
There are variations from the wild-type condition in either chromosome structure or chromosome number
Chromosomal aberrations
This mechanism is seen when genes are inherited only from the mother.
Genomic imprinting
Special form of duplication seen in Huntington’s Disease.
Expansion of trinucleotide repeats
Variation in Chromosome Structure
Deletion
Duplication
Inversion
Translocation
Three broad categories of chromosome mutations
Chromosome Rearrangements
Aneuploidy
Polyploidy
Overall chromosome number is unaffected, but large pieces of chromosomes move
Chromosome Rearrangements
Trisomy 21, Klinefelter’s Syndrome, Turner’s Syndrome
Aneuploidy
These mutations alter chromosome structure
Chromosome Rearrangements
One or more individual chromosome pair has its number altered (either add or subtract)
Aneuploidy
One or more complete chromosome sets are added
Polyploidy
3n, 4n
Polyploidy
T/F: Aneuploidies present as one or more of the chromosomes in the pair.
True
In what phase do aneuploidies occur?
Meiosis
This refers to a pair of homologous chromosomes that has failed to separate or segregate at anaphase so both chromosomes of the pair pass to the same daughter cell.
Nondisjunction
This refers to chromosomes which does not properly separate, leaving one or two sex cells with an extra chromosome or with one less chromosome.
Nondisjunction
This can occur after nondisjunction during the mitotic cell division.
Mosaicism
Chromosomal disorders caused by this results in one line of cells with a chromosomal aberration while other lines may stay unchanged.
Mosaicism
T/F: Egg with monosomic conditions do not proceed to further fertilization.
True
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2n + 1 = 7
Aneuploidy (Trisomy)
3n = 9
Polyploidy (Autotriploid) / Triploidy
2n = 6
Chromosome rearrangement (duplication)
Where can triploidies be found?
Plants
Chromosomal mutation that results in the doubling of a segment of a chromosome
Duplication
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2n = 6
Chromosome rearrangement (Duplication)
Forms of Duplication
Tandem
Reverse
Terminal Tandem
This duplication is observed with the repeats in Huntington’s Disease.
Tandem Duplication
This duplication is observed with inversed sequences.
Reverse Duplication
This duplication is observed in the tips.
Terminal Tandem Duplication
Unbalanced set of chromosomes, relative gene dosage is upset
Aneuploidy
Loss of a single chromosome copy
Monosomic
Extra copies of single chromosome
Polysomic
T/F: Most chromosome abnormalities are lethal, frequently in spontaneous abortions.
True
Exceptions of Lethal Chromosome Abnormalities
Trisomy 13, 18, 21, and Sex Chromosomes
T/F: An extra X or Y chromosome usually has a relatively severe effect.
False
mild effect
Mild effect of extra sex chromosome
1) X chromosome inactivation/Dosage Compensation
2) Not much (essential) on the Y
Part of a chromosome present twice
Duplication
ISCN stands for?
International System for Human Cytogenomic Nomenclature
Abbreviations: dup
Duplication
dup(17p12)
Charcot-Marie-Tooth type 1A
FORMATIVE: Symptoms of Charcot-Marie-Tooth Disease
- Hammertoes
- Muscle Weakness
- Foot Drop
- Paralysis
- Numbness or tingling
- Creeping sensation in the legs
Duplication that is one right after the other
Tandem duplication
Duplication that is repeated in another part of the chromosome (self explanatory daw)
Displaced Duplication
ABEFCD EFGH
Displaced duplication
ABCD EFEFGH
Tandem duplication
ABCD FEEFGH
Reverse duplication
T/F: Individuals can be homozygous or heterozygous for duplications, it can happen only on one or both sister chromatids.
True
Worst form of duplication
Homozygosity
consider dosage = more or lesser effect
The more or less there is will reflect on expression of phenotype
Dosage